1. Field of the Invention
The present invention relates to a light wavelength conversion unit and, in particular, a light wavelength conversion unit provided with a light wavelength conversion member that converts the wavelength of incident light and then emits the thus wavelength-converted light.
2. Description of the Related Art
In recent years, use of semiconductor light-emitting elements, such as light emitting diodes (LEDs), has grown very quickly in automotive headlamps, general illumination and so forth. When white light is to be obtained using such a semiconductor light-emitting element, a light wave conversion member is generally provided in a position facing a light emitting surface of the semiconductor light-emitting element that emits light such as blue light, near-ultraviolet light or short-wavelength visible light. Here, the light wave conversion member converts light excited by the light-emitting element and then emits light having a different wavelength. In order to increase the luminance of a light emitting device including the semiconductor light-emitting element, it is vitally important to not only increase the luminance of the semiconductor light-emitting element itself but also enhance the extraction efficiency of light by the light wavelength conversion member. Proposed is an illumination apparatus where a phosphor-containing member having an incident surface or emission surface, by which to enhance the extraction efficiency of light, used as a roughened surface is placed in a position facing the LED.
Even in the case of the aforementioned proposed illumination apparatus where the emission surface is used as the roughened surface, part of light in the emission surface is reflected inside the light wavelength conversion member. Such light reflected thereinside is partially guided through the interior of the member and reaches side faces thereof and therefore such light is finally emitted from the side faces as well. However, as light is emitted from the surfaces other than the emission surface, the amount of light emitted from the emission surface is reduced and therefore it is difficult to enhance the luminance of the emission surface.